Piston ring



March 23, 1965 D. w. HAMM 3,174,760

PISTON RING Filed March 19, 1962 INVENTOR. 0006146 M HAM/W 32 BYZaV M United States Patent 3,174,760 PISTON RING Douglas W. Hamm, Norton Township, Muskegon County, Mich, assignor to Muskegon Piston Ring Company, Muskegon, Micln, a corporation of Michigan Filed Mar. 19, 1962, Ser. No. 180,501 2 Claims. (Cl. 277-140) This invention relates to piston rings, and more particularly to an expander-spacer for piston rings.

The tendency in modern automotive engine construction is to shorten the stroke and increase the compression ratio. These conditions, together with the higher speeds and longer periods of continuous operation, have materially changed the demands which have been placed on piston rings. As a result of these conditions, it is important that the rings be highly flexible and responsive to cylinder wall shape. It is also becoming increasingly important to reduce the Weight of the rails and of the spacer-expander to a minimum. This is necessary to minimize the problems of momentum and inertia which are experienced at each end of the stroke, tending to unseat the rail from the sides of the groove. When this latter occurs, the sealing etfect of the ring is impaired, to a greater or lesser degree.

The increase in the compression ratio and the development of higher horsepower engines has greatly increased the pressures which are exerted against the rings. Thus, while it is desirable to decrease the weight of the rings, it is necessary to retain and often increase their original supporting strength.

This invention is designed to provide a solution to these problems. It effects positive support for the rails at the outer diameter of the spacer where the rails are subjected to maximum blow-by pressures. The invention also, by effecting positive support for the rails at this point, accurately spaces the rails adjacent their outer diameters, this assuring a constant, proper fit with the sides of the ring grooves adjacent the outer radial edge of the grooves.

This latter is most important since a substantial portion of the sealing efiected by the ring is designed to prevent by-passing of the ring by both combustion and crankcase gases. Control of blow-by and oil passage is effected in substantial measure by the fit between the rails and the sides of the ring groove, particularly adjacent the outer, radial portions of the ring grooves. By accurately spacing the rails at this point and by maintaining this spacing throughout the rings operating cycle, the pumping action which occurs when the position of the rails shifts at each end of the stroke is eliminated. This pumping action can, if not controlled, be a major cause of leakage of oil past the rings.

This invention accomplishes these purposes while permitting the structure of the expander spacer to be relatively light and open. The low weight of the expanderspacer reduces momentum and inertia. The openness of the ring prevents it from becoming clogged with carbon and similar deposits which interfere with relative movement between the rails and the spacer and with the proper flexing of the spacer and rails. Proper flexing and freedom of movement of the rails are necessary to effective sealing.

These and other objects and purposes of this invention will be understood by those acquainted with the design and manufacture of piston rings upon reading the following specification in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a plan view of the blank from which the spacer-expander is made;

FIG. 2 is a fragmentary ,oblique view of the fabricated spacer-expander;

FIG. 3 is a fragmentary, sectional, elevational view of a piston ring incorporating this invention;

FIG. 4 is a fragmentary, sectional, elevational view of a slightly modified form of this invention;

FIG. 5 is a greatly enlarged, fragmentary sectional view of the end of one of the rail supporting cars.

In executing the objects and purposes of this invention, there is provided a piston ring having rails which are held in position and placed under radial tension by a spacerexpander. The spacer-expander has rail seats and stops by which the radial force of the spacer-expander is exerted upon the rails. The spacer-expander also, at its radial, outer face, has a plurality of fingers which contact the inner side of the rail and positively support it adjacent its outer, radial edge. The structural arrangement of these fingers is such that they afford positive support for the rails, accurately controlling their position.

Referring specifically to the drawings, the numeral 10 refers to a blank which is initially formed as a continuous band of thin steel. The material for this band may be a spring steel but preferably it is of a steel which is made resilient by subsequent heat treating after the spacer-expander has been formed. The band has a plurality of annuli 11 spaced equidistantly from each other along its length. These annuli are elongated cross-wise of the band and are joined to each other by webs 12. The webs 12 are centered about the axial center line of the blank and form the only connection between adjacent annuli. The webs 12 are X-shaped, that is, they have the shape of a cross with a finger or ear 13 projecting from each side. The ears 13 are preferably arranged normal to the web. They are equally spaced from adjacent annuli, thus centering them in the gaps between the annuli.

To form the spacer-expander 20 from the blank 10, the outer ends of the annuli are bent over along the bend lines 14 and 14a. The bend lines 14 and 14a are parallel and equally spaced on opposite sides of the longitudinal center line of the blank. By this operation, the outer portions of the annuli 11 are formed into the rail supporting seats 21, one on each of the opposite, axial faces of the spacer. The closed ends of the annuli are also bent to form the rail stops 22. The rail stops project axially outwardly from the outer faces of the rail seats 21, and while they may be normal to the rail seats, preferably they are inclined slightly away from the rail seats, as shown in FIG. 3. The central portions of the sides of the annuli become the supporting legs 15 for the rail seats.

In the punching operation by which the initial blank 10 is shaped, it frequently occurs that the metal is slightly rounded where the shearing action of the punch occurs. This produces an edge surface 50 which is not perpendicular to the face 51 of the blank, as illustrated in FIG. 5. When this occurs, another part such as the rail 30 resting on the edge 50 in a position normal to the face 51 will only contact the high point 52 of the edge. This, under some operating conditions, is not desirable. To overcome this, the cars 13 may be bent to incline slightly toward the rail seats 21 (FIG. 3). This inclination will only be that which is necessary to make the surface 50 generally parallel to a fiat surface which is normal to the face 51.

The spacer-expander formed as described above is coiled into a circle to form a spacer-expander of annular shape. In the coiling procedure, the web members 12 become the radial, outer bight portion of the spacer-expander with the rail seats 21 extending radially, inwardly and terminating in the rail stops 22. In this structure it will be noted that the webs 12 form the means by which the spacer-expander is tied together since they form the only connection between adjacent annuli 11. At the 2.8 same time, theannuli, each having a large, central opening 23 which projects deeply into each of the rail seats,

forms a generally U-shaped spring, permitting flexing of the spacer-expander while at the same time providing suflicient strength to permit the spacer-expander to develop the necessary degree of radial tension which is applied to the rails through the rail stops 22. The. ends of the spacer-expander are butted at the part line 24.

To form the complete piston ring, a pair of rails 30 and 31 are mounted on the spacer-expander, one on each side. The radial, inner edge of the rails butts against the rail stops 22. The radial, inward inclination of the stops tends to bias the rails toward the adjacent side 32 of the ring groove 33; The radial tension generated by the spacer-expander 29, together with the radial tension inherent in the rails, forces the rails outwardly into sealing contact withthe cylinder wall 34. Adjacent the outer face of the piston, the rails are positively supported by the axial outer ends of the ears 13. The slight radial, inward inclination of the ears 13' causes the rails 30 and 31 to seat on all or substantially all of the end surface area of the ears rather than on the inner edge corner. This affords full support for the railsand. reduces the wear experienced by the ends of the ears.

However, where the condition illustrated in FIG. does not occur, or the operating conditions do not require substantially full face contactat the ends of the ears 13, the ears 13 maybe left straight. This condition is illustrated in FIG. 4.

The ears 13, together with the web portion 12 which extends between them, irrespective of whether or not'the ears 13 are slightly inclined, form What is for all practical purposes a straight pillar. Extending axially between the rails, they form a rigid support for the rails adjacent their outer radial periphery. This pillar, which is collectively identified in FIG. 3 by the numeral 34, forms a rigid and for all practical purposes-an incompressible separator for the rails, supporting them against compressive forces which would tend to shift the rails toward each-other. This support not only accurately spaces the rails when they are initially installed but maintains this accurate spacing even under the high compressive'loads resulting from both the inertial-momentum forces and the compressive forces exerted. by gases from the combustion chamber.

The pillars 34 support the rails independently of the spring members 21, materially reducing the loads applied to the spring members or. rail seats. Further, the support is provided where the loads are mostintense upon the rails, that is, adjacent the outer face of the piston. The structural weakness which is inherent in any structure in which loads have to be supported on an extended moment arm, such as: is true with the bent over rail seats 21, is eliminated. Since the pillars 34 are short and straight or 4 almost straight, the loads act through them in a straight line. Thus, relatively thin steel will be adequate to firmly support the rails, permitting the spacer to be made of lighter gauge materials. This contributes to a reduction in weight and thus of inertia and momentum generated by the mass of the spacer-expander itself.

It will be seen that this invention provides a simple, relatively inexpensive yet effective solution to the problem of accurate and positive support for the rails of a piston ring yet permits the spacer-expander to be fabricated of thin, relatively lightweight material.

While a preferred embodiment of this invention has been described, it will be recognized that modifications of this invention may be made. Such of these modificationsas incorporate the principles of the invention are to be considered as included in the. hereinafter appended claims, unless these claims by their language expressly state otherwise.

Iclaim:

l. A piston ringhaving a .pair of rails and a spacerexpander, said piston ring comprising: a circularbody having generally U-shaped spring members, a portion of each of which extend radially of said body to form a pair of axially spaced side seats for. said rails; said spring member s-being joined togetheralong the radial outer face of said body by circumferentially extending web elements; each of said web elements having axially extendingrailsupporting ears, said ears being arranged in pairs with the ears of each pair axially aligned and with one ear of each pair extending from each of the opposite sides thereof to forma-rigid pillar extending between the axially spaced planes of saidrail side seats; said ears contacting said rails along the radial periphery of said spacerexpander body and forming a continuous rigid spacing member between said rails; said rail seats and said pillars cooperating to provide both radial inner and radial outer axial support for said rails; an axially extending rail stop on the radial inner end of each of said spring members.

2. A spacer-expander as recited in claim 1 wherein said ears extend axially beyond the planes of said rail side seats and provide the sole support for said rails at the radial outer periphery of saidspacer-expanded body.

References'Cited' by the Examiner UNITED STATES PATENTS 2,827,349 3/58 Burns 277--l40 2,831,738 4/58 Marien 277-139 2,917,353 12/59 Baumler et al. 277139 XR EDWARD'V'. BENHAM, Primary Examiner. SAMUEL Q R a ne. 

1. A PISTON RING HAVING A PAIR OF RAILS AND A SPACEREXPANDER, SAID PISTON COMPRISING: A CIRCULAR BODY HAVING GENERALLY U-SHAPED SPRING MEMBERS, A PORTION OF EACH OF WHICH EXTEND RADIALLY OF SAID BODY TO FORM A PAIR OF AXIALLY SPACED SIDE SEATS FOR SAID RAILS; SAID SPRING MEMBERS BEING JOINED TOGETHER ALONG THE RADIAL OUTER FACE OF SAID BODY BY CIRCUMFERENTIALLY EXTENDING WEB ELEMENTS; EACH OF SAID WEB ELEMENTS HAVING AXIALLY EXTENDING RAIL SUPPORTING EARS, SAID EARS BEINNG ARRANGED IN PAIRS WITH THE EARS OF EACH PAIR AXIALLY ALIGNED AND WITH ONE EAR OF EACH PAIR EXTENDING FOR EACH OF THE OPPOSITE SIDES THEREOF TO FORM A RIGID PILLAR EXTENDING BETWEEN THE AXIALLY SPACED PLANES OF SAID RAIL SIDE SEATS; SAID EARS CONTACTING SAID RAIL ALONG THE RADIAL PERIPHERY OF SAID SPACEREXPANDER BODY AND FORMING A CONTINUOUS RIGID SPACING MEMBER BETWEEN SAID RAILS; SAID DRAIL SEAT AND SAID PILLARS COOPERATING TO PROVIDE BOTH RADIAL INNER AND RADIAL OUTER AXIAL SUPPORT FOR SAID RAILS; AND AXIALLY EXTENDING RAIL STOP ON THE RADIAL INNER END OF EACH OF SAID SPRING MEMBERS. 